Star.pngStar.pngStar grey.pngStar grey.pngStar grey.png

Tiger tail

From Roader's Digest: The SABRE Wiki
Jump to navigation Jump to search
Tiger tail
Catshill Interchange.jpg
A tiger tail merge on the M5 at Catshill Interchange
Cameraicon.png Pictures related to Tiger tail
View gallery (9)

The phrase tiger tail is informally used, even in engineering departments, to describe a ghost island used, typically, on motorway entry and exit slip roads.

TD22/06 of the Design Manual for Roads and Bridges defines one as a ghost island layout at a diverge utilising TSRGD diagram 1042.1 to separate the points of exit to a slip road. So called because the vertical sign used to inform drivers of the layout incorporates an illustration that resembles a tiger’s tail.

The use of such merging layouts has its origins at the beginning of the motorway system. A crudely designed ghost island merge, using different coloured surfacing rather than hatched road markings, was in place at the merge of the M1 and M45 in 1959. There were fears motorists would find this layout confusing, and large 'traffic islands ahead' warning signs were erected.

By the 1990s, this was still a cause for concern. TRRL said that compliance at M1/M25 was still very poor.

Their use was rather reserved until the 1990s, by which point they were used at M3 J2, M42 J3a, M6 J30 and M25 J7. In 1995 an official study examined three new setups: M6 J4a, M20 J3 and M27 J4.

The vertical traffic signs used at tiger tail diverges were only prescribed in the 2016 edition of the Traffic Signs Regulations and General Directions. Prior to this, all locations had to be specifically authorised by the Highways Agency, and the exact layout of each sign would vary.

Links




Tiger tail
Related Pictures
View gallery (9)
Catshill Interchange.jpgM1 J6a around 6 years ago - Coppermine - 16608.jpgJoining M4 - Coppermine - 16700.jpgM4 Junction 29 looking westbound at the A48(M) diverge - Coppermine - 12075.jpgA1(M) North, from St Albans Road, South Mimms - Geograph - 111856.jpg
Road Basics
Physical layoutSingle track • Single carriageway • Dual carriageway • High Quality Dual Carriageway • Road Widths • Urban Streets • Abandoned Road
Legal typesAll-purpose Road • Special Road • Motorway • Trunk road • Principal road • Classified Numbered road • Classified Unnumbered Road • Unclassified road • Primary Route • Non Primary Route • Right of Way • Unadopted road
Road numbers1922 Road Lists • Classification • Defunct road • Euroroutes • MoT Maps • National Cycle Network • Numbering principles • Numbering anomalies • Disputed Numbers • Recycled number • Unallocated numbers • Fictional Road Numbers • Junction numbers • Essential Traffic Routes
Road FeaturesArterial Road • Automatic Bollard • Balancing Pond • Belisha Beacon • Bott's Dots • Bypass • Cannon • Cats' Eyes • Cattle Grid • CD Lanes • Central Reservation • Chopsticks • Crash Barrier • Cuttings and Embankments • Cycle Lane • Emergency Phone • Escape lane • Expressway • Fingerpost • Flare • Ford • Gore • Green Bridge • Green Wave • Hairpin bend • Hard shoulder • Island • Junction • Layby • Level Crossing • Local Access Road • Managed Motorways • Milestone • Multi Lane Drop • Multiplex • No-Car Lane • Nose • Oxbow Road • Parapet • Petrol station • Play Street • Raised Pavement Markers • Ramp Metering • Retaining Wall • Road Studs • Roadside Art • Roadside Quarry • Roadworks • Secret motorway • Signage • Smart Motorway • Snow pole • Speed Limit • Spur • Street Lighting • Surface Dressing • Temporary terminus • Throughpass • Tidal Flow • Tiger tail • Toll booth • Traffic cone • Traffic Signals • Tunnel • Vehicle Recovery • Walking and Cycling Friendly Road • Weaving • Wig-Wag Signals • Winter Maintenance • Zip merge
Traffic CalmingBuild-Outs • Chicane • Dragon's Teeth • Home Zone • Low Traffic Neighbourhood • Pinch Point • Quiet Lane • Rumble strips • Safety Cameras • Sleeping Policeman • Speed bump
Public Transport FeaturesBus Lane • Bus stop • Guided Busway • Park and Ride • Tramway • Trolleybus System
Other termsAnderson report • Guildford Rules • Highway Authority • Highway Code • Model Traffic Area • Motorway alphabet • Pre-Worboys • Primary Destinations • Roads by 10 • Transport alphabet • Worboys report
AcronymsAADT • ADS • ANPR • ATM • DfT • GSJ • HA • HATO • HE • HETO • HQDC • LAR • LILO • LTN • MOVA • NCN • NMU • NRA • PBU • POPE • PTS • PFI • RCS • SABRE • SCOOT • SSD • SON • SOX • SRN • TEN-T • TERN • TfL • TII • TOTSO • TRO • TSM • TSRGD • UTC • VAS • VMS • VSL

SABRE - The Society for All British and Irish Road Enthusiasts
Discuss - Digest - Discover - Help